h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Argh - I can't find it! It's in yesterday's Irish Examiner... I'll keep a look-out however. I have an entry in Peer Review at the moment on the Storegga Tsunamis A2756720 - its about a set of tsunamis which were caused by a likely gas hydrate release off the coast of Norway, many many years ago.

And just when you thought it was safe to go back into the water!

Woodpigeon

Do you know, i never knew about this one! What a find! Have you heard of any legends telling about this event? Any accounts might have been swamped by The Flood of the OT though. Happy disentangling!

I guess its such a long time ago - paleolithic or mesolithic - that legends would well have disappeared by now. Its still and interesting point though! I heard about it from a group of geologists I know. Stories like that are my sort of brain-food, and I just *had* to know more!

There is of course the later story of Doggerland - which is possibly more impressive than the OT flood. The whole area connecting northern Germany and Denmark to the UK was once above water, and one of the books that I read suggested that a great inundation took place in Northern Europe creating the southern North Sea in a very short period of time once the Ice Age glaciers started to retreat in anger. I must check out the book I read this from again. Sounds like I might have another Edited Guide article coming on!

Yes about the north sea I knew, but I thought it was a long process rather than a sudden flood? On the other hand, I heard of sunken trees on Doggerland, so you might be right after all. Yes please do an entry about that!

I'm in the UK today, but back in Cork tonight - I'm going to do some reading up when I get back. I don't think it was a sudden flood, but the author did mention that it would have been fast enough for there to have been a great displacement of people. Even an event over years or decades would do this.

I wonder where I heard that tale of ship's keels scraping on the treetops of doggerland. It's only 13 m deep there.

I checked my reference - its fairly fascinating. It wasn't sudden like the Black Sea, but what it did entail was something a bit like the global warming fiasco we are facing at the moment. Scientists do belive that over around 24 generations - whats that, 600-700 years or so; the indunation of Doggerland was complete. Around that time you also had sudden catastrophes such as Storegga, and the release of the Baltic Ice Lake. I'm not yet ready to do an entry on it yet however - I think I have much more reading to do to understand it better.

Ah the global warming, is that as certain as the global cooling was in the 70ies? At least the very same people are absolutely certain of it. Seems an article of faith sometimes, so there must be heretics!

I sometimes think why do we have to decide if we're heating up or cooling down, or wether that's normal or abnormal. There's no doubt the glaciers are retreating, and as they do that what do they release? Tree trunks, and not conifers either, but leafy trees.
Or wether that's good or bad. The ice bears say it's bad, the camels in Mauretania say it's good, because now it's raining there sometimes.

Should just agree that it's a bad idea to release within a 100 years all the carbon fixed 150 Million years ago over a period of a coupla million years, would be more to the point?

There, just mention global warming, and off i go! Don't mind me, will ya! Do you have a reference of the Baltic ice lake? I wish you would write that entry soon!

I would have been happy to sit on the fence regarding global warming, except that I got into the habit of looking through BBC Science and Nature articles for a few months, and eventually, due to the large amount of papers written on this subject, the argument for an ongoing warming is very difficult to disprove - there is oodles of data now around to support it. What is still up for debate are the causes - the world has gone through lots of warming and cooling phases before, none of them man-made. However, as you say, it does seem likely that releasing loads of fossil carbon into the atmosphere in such a short period of time is not good for us - so the argument for man-made warming is, at the very least, a reasonable one.

Models show that when glaciers retreat, the albedo effect of Earth is reduced, so more sunlight gets through, and more warming happens. The reverse happens during an ice age. There is also some evidence to show that the bad thing is not stable warmth or stable cold per se, but the instabilities caused during a transitional period - particularly the effect of decreasing habitats, plant failures, new introductions, diseases etc.

I'll try to get the name of that Baltic ice lake for you!

I do have a subjective feeling that there's a shift ocurring, what with more storms and unseasonal droughts or rains. But as to the reason for that? Even if it was the effect of greenhouse gasses already, carbon dioxide would only be one part of the phenomenon, and i don't see how we can curb for instance methane, as it comes mainly from paddy rice and cows, and those Asians simply insist on eating, so selfish of them, and I love my steak medium, which is tedious of me.
And who knows, maybe the carbon dioxide is good for the trees? They need a break, poor things, and in fact do look uncommonly lush to me lately.
There you go, heretic mode again.
Seriously now, lookin at National Geographic's latest issue, there was that dramatic curve of how carbondioxide had increased. Then i noticed that they had slashed 9/10 of the y-axis of the graph, so any little change would show up as a fearful jump and i still wonder what the effect actually would be, if any. Also was only over the last 100 years...
That reminds me, i must get around to look up the research results of those ice drillings, to see how co2 fluctuated over the past million years or so. *Makes note*

Looks like it was just called the Baltic Ice Lake, but then there were two salt-water inundations before the Baltic Sea appeared: one was the Yoldia sea, the other was the Anchylus Sea - I could have got the spelling of the last one wrong.

Tut, tut - Nat Geo doing the old "cut the y-axis" trick? That irritates me too.

Methane from cows and intensive rice production are also man-made - the cows we breed today are super-sized relatives of the original cows: born food factories. Rice is as old as the hills: but the population it feeds is enormous. However, on the other side, volcanic eruptions can have a starkly cooling effect on the planet, and we haven't had any biggies for a while now. I'd be interested in what you dig up regarding ice-core data.

I'm at the moment slogging through the nature articles about the Ice Core Data http://www.nature.com/nature/links/040610/040610-1.html.

* note to self - try again to find out how to get access to my college's journals!

oh durn, i somehow managed to get the pdf file without registering ... it's all rather intricate, about earth axis and length and average temperature of interglacials ... ok i'll slog and then i tell you

All right, here we go, some of the salient points from those ice core data (ICD)
First to greenhouse gasses. Over the last 400 ky or so concentration of CO2 and CH4 has fluctuated considerably, but always between fixed maximum/minimum values, that is between 180 to 280-300 and 320-350 to 650-770 ppm respectively, the low values being in the glacials.
Pre-industrial levels were 280 and 650 respectively. Present days levels of 360 and 1700 ppm are unprecedented for the last 420 ky.
OK.
There are some interesting facts about glacial/interglacia rytms that have to be taken into account.
Interglacials in the last 400 ky lasted from 10 000 to 15000 years. Our present interglacial has lasted 12000 years already. Taking into account that the (preindustrial) CO2/NH4 concentration had already reached peak values, there is an indication that our interglacial might end in a few thousand years.
Now some scientists say that our interglacial would last about 30 ky, because the glacial rythm was changing again. I can't see how they make that out. Its true that in the time from 740 to 400 ky ago the interglacials were longer, 20 ky to 50 ky and that there was a rythm change about 400 ky ago, towards shorter interglacials. But the longer interglacials also were cooler, so that the transition from glacial to interglacial was much less marked. It is true that the warmest interglacial temperature of the last 400 ky was slightly higher than the Holocene, but the Holozene temperature is still well within the limits of the last 4 cycles.
These are the facts i gleaned so far, and I leave it to you interprete them, thusly I virtuously refrain from speculating.

You've been diving into Milankovic cycles then? The story of Mr. Milankovic is a really extraordinary one. Basically they act as predictors to the next ice age, by using all the long-term rotationary effects and the positions of continents on the earth to predict how heat disperses itself across the globe. The ice core and ocean core data match up well to the mathematical models predicted by Milankovic. I was of the understanding that we were about half-way through the current inter-glacial.

The concentrations of greenhouse gasses is certainly worrying. Have they identified any micro trends comparing the last inter-glacial with the current one? After all we are only talking about a 200 year period in this inter-glacial - how do temperatures in the last 200 years, or last 100 years match to the highest temperatures of the last interglacial? Am I making any sense?

Well as I said earlier, far as I understood the data ours isn't the warmest interglacial yet, there was one before with higher temperatures, I mentioned the foliage trees found in the retracting glaciers of the Alps.

Not that i want to trivialise the current development re the socalled greenhouse gasses, have to be very careful not to sound like that, just because I'm irritated with the worry merchants. I think it's a bad idea to burn up all the fossilised carbon at a far greater rate than the green plants and the oceans are capable of fixating it, all I'm saying is that nobody can predict what the results will be. But stands to reason if we raise CO2 to Silurian levels, we'll get ... Silur eventually. Dunno if that would be good or bad, but as you remarked, it's the transition that's so hazardous because it promises to be tumultuous.
But it looks to me that we have no idea really were it is going, the current data seem to allow two diametrically opposed interpretation:

1. The current interglacial is goin to last 20+ ky, temperatures are on a natural upswing, and we are creating an artificial interference accelerating that course, which will lead to overheating of the planet with melting of the ice cap and flooding.

2. The high pre-industrial values of CO2 and MH4 indicate that our interglacial is nearing it's end, and a new ice age is not too far round the corner. However, the unprecedented levels of greenhouse gasses create an interference that will smooth the temperature trough, keeping Northern Europe and America from freezing over.

Inbetween one can imagine different scenarios. I personally incline towards something like 2 on the grounds of what we know of the past glacial cycles. I do however wonder how much atmospheric disturbance we can expect in the future.

Ok - are there strong scientific indications that we might be closer than we think to an Ice Age, taking the issue of the gulf-stream closing down aside?

looking at the diagrams of the last ice ages i thought the indications were rather strong, what with the glacial rythm and the tempreature increase, preindustrial, mind!

About time we got some snow here!